Nitrosocyclohexane dimer

After the reaction mixture is diluted with water, the product is separated by repeated extraction with ether. The ether solution is evaporated and the residual product is dried on an unglazed clay plate. The yield of nitrosocyclohexane dimer is 0.07 gm (26 %), m.p. 116°-117°C after recrystallization from acetone. 

Thus, in this particular system, reaction in liquid sulfur dioxide at —30°C leads to trans-l-chloro-2-nitrosocyclohexane dimer exclusively. 

In carbon tetrachloride at 20°C, only a small amount of the expected 1-chloro-2-nitrosocyclohexane dimer was formed. The major product fraction... 

Preparation of cis-exo-2-Chloro-3-nitrosonorbornane Dimer. 2-8. Preparation of cis-exo-2-Bromo-3-nitrosonorbornane Dimer. 2-9. Preparation of tra.ns-l-Chloro-2-nitrosocyclohexane Dimer (trans-2J -Dichioro-... 

Chloro-2-nitrosooctane 4-Chloro-4-nitroso-2,6-dimethylheptane 6-Chloro-6-nitrosoundecane 1 -Chloro-1 -nitrosocyclopentane 1 -Chloro-1 -nitrosocyclohexane 1 -Chloro-1 -nitroso-2-methylcyclohexane 1 -Chloro-2-ni trosocyclopentane dimer 1 -Chloro-4-nitroso-2-cyclopentene dimer l-Chloro-2-nitrosocyclohexane dimer... 

In carbon tetrachloride at —30°C the product mixture consisted of 95% of trans-1 -chloro-2-nitrosocyclohexane dimer and 5% of trans-1 -nitro-2-nitroso-cyclohexane dimer. In trichloroethylene at —30°C, a 50-50 mixture of these two products was formed [15]. 

An interesting proof has recently been given of photochemical splitting of free radical NO2 from nitroalkane Marciniak and Paszyc [62] irradiated nitro-methane dissolved in cyclohexane and received nitrosocyclohexane dimer ... 

A soln. of cyclohexene in isoamyl nitrite added at 5° with vigorous stirring during 2 hrs. to formic acid m 5 -l-formoxy-2-nitrosocyclohexane dimer. Y 59%. -Nitrosyl formate is prepared in situ. F. e. s. H. C. Hamann and D. Swern, Am. Soc. 90, 6481 (1968). 

A more recent kinetic study has indicated that under acidic conditions a-ketonitrosoalkanes may rearrange rapidly to the oxime [33]. Amines also bring about the isomerization of nitrosocyclohexane [34], These observations along with the older observations mentioned in Touster s review [2] imply that the whole question of the nitrosation of aliphatic carbon atoms should be reexamined with modern techniques to establish the reaction conditions under which the true aliphatic nitroso compounds (or their dimers) can be isolated. 

In another system recently proposed, the trans isomer of dimeric 1-chloro-2-nitrosocyclohexane would be called Dms-2,2 -dichloro-rra .y-azodioxy-cyclohexane [15,16]. In line with a system used in naming azoxy compounds, the dimers may also be named as diimide dioxides. 

As in other areas of the chemistry of nitroso compounds, the tacit assumption has been that the rearrangement of aliphatic nitroso compounds bearing hydrogens on the carbon atom which also carries the nitroso group rearranges to the oxime virtually instantaneously. Yet, recently, the existence of all types of aliphatic nitroso compounds has been well established. Without going into details here, nitrosomethane, nitrosocyclohexane, and nitrosodibenzoyl-methane have been prepared and appear to exist as reasonably stable dimers. 

MCPBA has been regarded as the reagent of choice for the conversion of primary aliphatic amines into the corresponding nitro compounds. The peroxy acid must be used in excess to minimize formation of dimers of the intermediate nitroso compounds, llie yield of nitroalkane is also increased if the reaction is carried out at elevated temperature, since this favors the monomeric rather than the dimeric foim of the intermediate nitrosoalkane and allows it to be oxidized further. For example, cyclohexylamine gave the dimer of nitrosocyclohexane (43%) when oxidized by MCPBA at 23 C, but at 83 C (in boiling 1,2-di-chloroethane) the only product was nitrocyclohexane (86%). 

Aliphatic primary and secondary nitroso compounds are not stable but tautomerize to oximes. In nitrosocyclohexane the special steric conditions favor a dimerization rather than a tautomerization. The dimer is reduced polarographically in a six-electron reaction to A, A -dicyclohexylhydrazine [71]. Aliphatic Miitro compounds are dimers in the solid state, but dissociates in solution to a degree depending on the solvent the monomer is easier reducible than the dimer [72]. Only the monomer reacts as a spin trap the rate constant for the dissociation in MeCN is 1.5 x 10" s" [72a]. 

Replacing the nitrosyl chloride by a mixture of nitric oxide and chlorine has also proved successful in the nitrosation of irradiated saturated hydrocarbons. According to the conditions and the proportions in which the oxide and chlorine are used, cyclohexane affords as main product 1-chloro-l-nitroso-cyclohexane, dimeric nitrosocyclohexane, or cyclohexanone oxime. Experimental details of this interesting reaction, which has industrial interest, will be found in a review by Muller et ah212 and the papers cited therein. 

---